Inflatable imbibed polymer devices

ABSTRACT

The present invention provides a stretchable material suitable for use in an inflatable medical device. The stretchable material has at least one reinforcing polymer layer with a top and bottom side forming a porous matrix which is imbibed with a sealing material to infiltrate and substantially seal spaces of the porous matrix and extend beyond the reinforcing polymer layer to form a surface coating.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/204,902, filed Jul. 7, 2016, now U.S. Pat. No. 9,878,133, issued Jan.30, 2018, which is a continuation of U.S. patent application Ser. No.14/918,845, filed Oct. 21, 2015, which is a divisional of U.S. patentapplication Ser. No. 11/500,794, filed Aug. 7, 2006, now U.S. Pat. No.9,180,279, issued Nov. 10, 2015, all of which are incorporated herein byreference in their entireties for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates to a unique material suited for use inballoon catheters and, more particularly, to a low profilenon-shortening wrapped balloon configured to expand to a predetermineddiameter upon application of a predetermined pressure thereto. Theunique properties of the material of the present invention enablewrapped balloons to be made without the use of internal bladders.

Balloon catheters are well known in the art. Such catheters are employedin a variety of medical procedures, including dilation of narrowed bloodvessels, placement of stents and other implants, temporary occlusion ofblood vessels, and other vascular uses.

In a typical application, the balloon is advanced to the desiredlocation in the vascular system. The balloon is then pressure-expandedin accordance with a medical procedure. Thereafter, the pressure isremoved from the balloon, allowing the balloon to contract and permitremoval of the catheter. It is to be appreciated that prior art balloonsare typically formed of an elastomeric material which is readilypressure-expanded, and also readily contracts upon removal of theinflation pressure.

Some catheter balloons constructed of both elastomeric andnon-elastomeric materials have been described previously. U.S. Pat. No.4,706,670 describes a balloon dilatation catheter constructed of a shaftmade of an elastomeric tube and reinforced with longitudinal inelasticfilaments. This device incorporates a movable portion of the shaft toenable the offset of the reduction in length of the balloon portion asthe balloon is inflated. A major drawback to balloons of this type isthe need for a bladder which increases the profile of the balloon.

Traditionally, a fluoropolymer matrix which is filled with a coatingthat does not extend outside the matrix permits the coating to pull awayfrom the matrix causing holes that eventually demonstrate themselves ina “weeping” manner on the balloon. This is believed to be due to theinadequate adhesion strength between the matrix and the coating as wellas the stress concentrations at those interfaces.

There is a need in the art for a low profile wrapped balloon which doesnot lengthen or shorten upon inflation and has the ability to withstandinflation pressure strain without disruption, while still remainingwatertight without the use of a separate bladder that adds to theballoon profile. The present invention fulfills this need by providing aunique material which allows for the elimination of a bladder. It alsoallows the balloon to readily expand under pressure without leaking.

SUMMARY OF THE INVENTION

The present invention provides a stretchable material comprising areinforcing polymer having a porous matrix with void spaces and asealing material imbibed into the reinforcing polymer substantiallysealing the porous matrix void spaces and extending beyond thereinforcing polymer matrix to form a surface coating that can bestretched without the occurrence of holes through the thickness of thematerial. In a preferred embodiment, a low angle wrapped catheterballoon is comprised of a material which stretches primarily in onedirection and less than 54.7 degrees is formed with said material. Asthe balloon is inflated to its working diameter, the wrapped materialrotates towards the balanced force angle of 54.7 degrees. When rotating,the wrapped material also strains perpendicular to the length of thewrap according to the following geometric relationship(Width_(F)=Width_(I)×(cos θ_(F)/cos θ_(I))²×(tan θ_(F)/tan θ_(I)) whereF is Final and I is initial. This strain can exceed 500 percent in someballoons depending on the deflated to inflated diameter ratio. Thepresent invention allows for this strain to occur without inducing holesor compromising the sealing coating. The material is suitable for liquidor gas impermeable applications.

The present invention further provides a balloon catheter comprising atubular catheter shaft having a longitudinal axis and an inflatablebladderless wrapped balloon affixed to the catheter shaft wherein theballoon comprises at least one reinforcing polymer layer with a top andbottom side forming a porous matrix, said porous matrix is imbibed witha sealing material that infiltrates and substantially seals void spacesof the porous matrix and extends beyond the reinforcing polymer layer toform a surface coating. The surface coating is formed on at least oneside of the reinforcing polymer layer.

The present invention yet further provides a balloon catheter with asurface coating thickness which is modulated to allow for controlledporosity when strained due to inflation.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show cross sections of a reinforcing polymer. FIG. 1A isthe reinforcing polymer prior to imbibing. FIG. 1B shows the imbibedreinforcing polymer with two surface coatings.

FIG. 2 shows a cross section of a reinforcing polymer with a singlesurface coating.

FIG. 3 shows a composite film wrapped at a low angle on a release coatedcore wire.

FIG. 4 shows a cross section of a balloon material layer wrapped on awire.

FIG. 5 shows a bladderless balloon with a heat treated inflation region.

FIG. 6 shows a schematic diagram depicting attachment via two sealingmeans of a bladderless balloon to a hypotube.

FIG. 7 shows a cross section of a single coated anisotropic materialFIG. 8 shows a cross section of a bladderless balloon for fluid deliveryat higher pressures.

FIG. 9 shows non-distensible seal wrapped onto a balloon material layer.

FIG. 10 shows a cross section of a non-distensible seal wrapped onto aballoon material layer.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that a reduction in the profile of prior art balloonsusing elastomeric bladders and outer reinforcing materials can beachieved using the materials of the present invention. The material ofthe present invention combines a reinforced matrix with elastomericproperties. This unique combination allows balloons to be formed withoutthe need for a separate elastomeric bladder, thus providing reducedprofiles. The present invention provides a reinforcing polymer suitableto withstand strain in one or more directions without leaking, and iswell suited for medical devices and inflatable devices. The material isparticularly well suited for catheter balloon applications requiring asmall initial profile for entry into a vessel. The material ispreferably stronger in a longitudinal direction as opposed to itstransverse direction.

There are numerous porous membranes which would be suited to use for animbibed polymer. As shown in the following examples, ePTFE has been usedto demonstrate the present invention based upon preferred properties ofthinness and drapability. While reinforcing polymers with anisotropicproperties are preferred for embodiments such as catheter balloons, anisotropic reinforcing polymer may be desired for other imbibed materialembodiments.

As shown in FIGS. 1A and 1B, the reinforcing polymer 1 comprises atleast one matrix 20 with void spaces 21. The matrix should have a topside 25 and a bottom side 26. A sealing material 3 is imbibed into thereinforcing polymer 1 to form an imbibed reinforcing polymer 2. Thesealing material 3 substantially seals the porous matrix void spaces 21and extends beyond the reinforcing polymer matrix 20 to form a surfacecoating 4 on one side of the reinforcing polymer 1, as shown in FIG. 2;or both sides of the imbibed reinforcing polymer 2, as shown in FIG. 1A.The sealing material 3 must be of a sufficient quantity not only to sealvoid spaces in the reinforcing polymer, but to extend beyond the matrixof the reinforcing polymer and form a continuous layer as a surfacecoating 4. The surface coating forms a continuous layer that is freefrom holes and extends beyond the matrix of the reinforcing polymer. Thereinforcing polymer may be comprised of any porous polymer, includingbut not limited to fluoropolymers, polyamides, polyesters,polycarbonates, microporous polyolefins, or UHMW polyurethanes. Thematrix can be that of a form typical of any oriented matrix, includingePTFE.

The composite film of the present invention comprises a porousreinforcing layer and a continuous polymer layer. The porous reinforcingpolymer layer is preferably a thin, strong porous membrane that can bemade in sheet form. The porous reinforcing polymer can be selected froma group of polymers including, but not limited to, olefin, PEEK,polyamide, polyurethane, polyester, polyethylene, andpolytetrafluoroethylene. In a preferred embodiment, the porousreinforcing polymer is anisotropic such that it is highly oriented inthe one direction. An ePTFE membrane with a matrix tensile value in onedirection of greater than 690 megapascals is preferred, and greater than960 megapascals is even more preferred, and greater than 1,200megapascals is most preferred. The exceptionally high matrix tensilevalue of ePTFE membrane allows the composite material to withstand veryhigh hoop stress in the inflated balloon configuration. In addition, thehigh matrix tensile value of the ePTFE membrane makes it possible forvery thin layers to be used which reduces the deflated balloon profile.A small profile is necessary for the balloon to be able to be positionedin small arteries or veins or orifices. In order for balloons to bepositioned in some areas of the body, the balloon catheter must be ableto move through a small bend radius, and a thinner walled tube istypically much more supple and capable of bending in this manner withoutcreasing or causing damage to the wall of the vessel.

In another preferred embodiment, the ePTFE membrane is relativelymechanically homogeneous. The mechanically balanced ePTFE membrane canincrease the maximum hoop stress that the composite film made therefromcan withstand.

The continuous polymer layer of the present invention is coated onto atleast one side of the porous reinforcing polymer. The continuous polymerlayer is preferably an elastomer, such as, but not limited to, aromaticand aliphatic polyurethanes including copolymers, styrene blockcopolymers, silicones, preferably thermoplastic silicones,fluoro-silicones, fluoroelastomers, THV and latex. In one embodiment ofthe present invention, the continuous polymer layer is coated onto onlyone side of the porous reinforcing polymer. The continuous polymer layeris coated onto both sides of the porous reinforcing polymer. In apreferred embodiment, the continuous polymer layer is imbibed into theporous reinforcing polymer and the imbibed polymer fills the pores ofthe porous reinforcing polymer.

The continuous polymer layer can be applied to the porous reinforcingpolymer through any number of conventional methods including, but notlimited to, lamination, transfer roll coating, wire-wound bar coating,reverse roll coating, and solution coating or solution imbibing. In apreferred embodiment, the continuous polymer layer is solution imbibedinto the porous reinforcing polymer. In this embodiment, the continuouspolymer layer is dissolved in a suitable solvent and coated onto andthroughout the porous reinforcing polymer using a wire-wound rodprocess. The coated porous reinforcing polymer is then passed through asolvent oven and the solvent is removed leaving a continuous polymerlayer coated onto and throughout the porous reinforcing polymer. In somecases, such as when silicone is used as the continuous polymer layer,the coated porous reinforcing polymer may not require the removal ofsolvent. In another embodiment, the continuous polymer layer is coatedonto at least one side of the porous reinforcing polymer and maintainedin a “green” state where it can be subsequently cured. For example, anultraviolet light (UV) curable urethane may be used as the continuouspolymer layer and coated onto the porous reinforcing polymer. Thecomposite film comprising the porous reinforcing polymer and the UVcurable urethane continuous polymer layer can then be wrapped to form atleast one layer of the balloon and subsequently exposed to UV light andcured. A pass is a number of layers applied in a wrapping event. A layermay comprise a single layer of composite film wrapped around theballoon.

Some typical examples of the reinforcing polymer can generally be foundat U.S. Pat. No. 5,476,589 and U.S. patent application Ser. No.11/334,243. The surface coating is of a sufficient thickness to maintaina watertight matrix when the sealing material is stressed, inflated, orstrained. The sealing material 3 is typically an elastomeric polymer orviscous flow material, such as an elastomer, urethane, fluoropolymer,nylon, polyether block amide, PEBA, or other suitable material.

In one embodiment, a catheter balloon may be constructed which changesin diameter by up to 700 percent. During the diameter growth, theballoon wraps rotate towards the balanced force angle of about 54.7degrees, while the elastomer imbibed reinforcing polymer will strainperpendicular to the wrap length up to 400-500 percent. This aspect isunique, the perpendicular strain caused by the rotation to the balancedforce angle allows higher radial elongation of the balloon at lessstrain on the elastomer, as compared to a balloon created from theelastomer alone. This attribute of the present invention providesimproved balloons with better recovery and which are of a higherstrength and higher burst pressure than traditional balloons. Further,the diameter of the elastomer balloon may be formed to limit thediameter growth once the balanced forces angle is reached. This alsoallows for symmetrical inflation of the balloon.

The wrap layers when configured in accordance with the present inventionform a balanced force angle which prevents the layers from incurringtransverse strain as the balloon inflates. Transverse strain is thetendency for individual material layers to stretch or strainperpendicular to the wrap angle. For this reason, anisotropic materialsare used which are highly oriented in the direction of the wrap angle toallow for the strain in the perpendicular direction. Additionally, theballoon exhibits essentially radial symmetry upon inflation. The balloonis wrapped by winding layers at opposing directions to one another untila desired thickness is obtained. The balloon material passes may becomprised of the same materials or different materials. While thethickness of the materials may vary, for vascular use it is advantageousto use balloon material that is less than 2 micrometers thick.

The following equation is useful for predicting the amount of transversestrain upon the elastomer imbibed reinforcing polymer during inflationof a balloon catheter of the present invention:initial width/final inflated width=1/(cos α_(f)/cos α_(i))²×(tanα_(f)/tan α_(i))

-   -   wherein α is defined as the angle between the longitudinal axis        of the balloon and the angle of the wrapped elastomer imbibed        reinforcing polymer.

In certain applications, it may be desirable that the surface coating isformed at a thickness which allows for controlled porosity when straineddue to inflation. Such controlled porosity allows delivery of a liquidin therapeutic quantities. The combination of the surface coating 4 andthe imbibed reinforcing polymer 2 provides a composite film 5. Thecomposite film 5 has a surface coating possessing a greater straincapability than either the sealing material 3 or the reinforcing polymer1 alone. In certain preferred embodiments it is desirable to use ePTFEas the reinforcing polymer 1. To produce a thin strong reinforcingpolymer with a desired mass and thickness, the polymer is expandedlongitudinally and transversely prior to imbibing with a sealingmaterial 3. The longitudinal expansion ratio is greater than thetransverse expansion ratio. As shown in FIG. 3, the composite film 5 ofthe present invention is suited for use as a balloon material layer 8.The composite film 5 can be cut or formed in longitudinal strips ornarrower pieces suitable for wrapping the composite film around a corewire 6 or mandrel with or without a release coating 7. The angle of thewrap can vary depending upon the desired attributes of the finishedballoon. Several different areas of differing wrap angles may exist onone balloon. In one desired embodiment the wrap angle of the compositefilm is between 2 and 54 degrees with respect to the longitudinal axisof the balloon, and more preferably less than ten degrees with respectto the longitudinal axis of the balloon. The composite film can bewrapped at an angle with respect to the longitudinal axis which promotesinflation to a defined diameter, then wrapped in a reverse direction atan opposing angle to the first pass for a plurality of passes formingdirectional layers. Upon inflation, the layers of opposing directionsform a balanced force angle approaching 54 degrees relative to eachother. As shown by the cross section in FIG. 4, the balloon materiallayer 8 can be wrapped in layers around the core wire 6 (or around arelease coating 7 on the wire) to form a tubular structure suitable foruse as an inflatable balloon when sealed at the ends. The tubularstructure may be subjected to heat and inflation pressure to form abladderless balloon with or without the use of a mold. The balloon ofthe present invention does not require a bladder, but may be constructedwith a bladder if desired. In one embodiment the balloon is comprised ofat least two helically oriented wrap layers which form an angle ofapproximately 54 degrees with respect to each other upon inflation. Thisangle allows the forces within the filament wound pressure vessel to beat equilibrium. The inflatable balloon of the present invention furtherexhibits radial symmetry upon inflation and non-foreshortening. Bynon-foreshortening it is meant that the length of the balloon does notchange by more than ten percent (more preferably 5 percent and even morepreferably 2 percent) upon inflation to a rated burst pressure. As shownin FIG. 5, the composite film 5 can be used as a balloon material layer8 and formed into a bladderless balloon 9 suitable for use as acatheter. Upon inflation, the inflated region 10 expands into apredetermined shape.

FIG. 6 shows a balloon catheter device 9 with a bladderless balloonattached to a hypotube. The bladderless balloon is attached to thehypotube or catheter shaft via a seal or other sealing means 13. Thematerial of the present invention may be used as the sealing means. Forexample in the present invention the sealing means holds the balloonmaterial layer 8 in contact with the hypotube 11 so that the balloon maybe inflated without pressure loss. The hypotube 11 has a longitudinalaxis around which the inflatable balloon is affixed. The hypotube mayfurther comprise a hypotube wrap layer 12 surrounding the hypotube. Whenthe hypotube wrap layer is present, the balloon material is affixed tothe hypotube wrap layer via a sealing means to form a seal.

FIG. 7 shows a reinforcing polymer 1 imbibed with a sealing material 3to form an imbibed reinforcing polymer 2 having a double surface coating4 layer, and forming a stretchable anisotropic material. A singlesurface coating may be used when only one side of the material wrap isdesired to be coated. The surface coating may be present on the insidesurface or the outside surface of the balloon.

In another embodiment, FIG. 8 shows a cross section of a bladderlessballoon having a surface coating of a thickness allowing for controlledporosity when strained due to inflation. Controlled porosity allowsdelivery of a liquid 15 from one side of the imbibed reinforcing polymerto the other side. The controlled porosity is a tortuous path, therebyallowing the therapeutic liquid to weep, (form droplets on the surfaceof the balloon). In another embodiment, the bladderless balloon having asurface coating of a thickness allowing for controlled porosity, weepsonly at high pressure. As shown in FIG. 8, the imbibed reinforcingpolymer 2 has at least one surface coating 4 formed by the sealingmaterial 3. The imbibed reinforcing polymer is formed into a bladderlessballoon 9 having stretchable anisotropic material 14 properties. Whenthe bladderless balloon is inflated by a fluid, small openings occur inthe surface coating which allow movement of the fluid from the interiorside of the balloon through the imbibed reinforcing polymer 2 to theoutside of the balloon. Delivery of therapeutic liquid agents may befacilitated using a bladderless balloon comprised of an imbibedreinforcing polymer with a controlled porosity. This controlled porosityis able to withstand pressures greater than 10 p.s.i., before allowingfluid movement from the interior to the exterior side of the balloon.

FIG. 9 shows that the bladderless balloon may be constructed to includeat least one non-distending layer 7 to provide a desired shape to thebladderless balloon or to provide a continuous integrated seal on aninflatable balloon. The continuous integrated seal may be formed byusing or providing a first balloon material layer 8 which is configuredto form a desired balloon shape. The sealing material may be a balloonmaterial layer 8, as such, an ePTFE reinforcing polymer imbibed withsealing material 3. The balloon shape is then wrapped with a wrap layeraround said first balloon material layer so that the angle of the wrapchanges to wrap at least one wrap layer at an angle sufficient to createseal over the first balloon material layer upon inflation. A secondballoon material layer may then be wrapped around the seal to increasethe bonding surface area of the seal if desired. In this manner the sealis located between two balloon materials to provide a gentle failuremode on a bladderless balloon. The material composite may be used tocomprise the non-distensible regions. As shown in FIG. 9, the core wire6 may be provided with a release coating 25. The release coating may beof a desired thickness to provide a desired inner diameter on thefinished balloon. The release coating has a balloon material layerwrapped and set around the core wire 6 to provide a bladderless balloon.

FIG. 10 provides a cross section of a non-distensible seal on abladderless balloon. The non-distensible seal is integrated as a wraplayer on top of the balloon itself. It may be wrapped at the same timeas the bladderless balloon by adjusting the wrap angle of the compositefilm wrap. The balloon material layer 8 is then wrapped with anon-distending layer 7 in desired areas to provide the bladderlessballoon with non-distending regions, as shown in FIG. 9. Thenon-distending regions should be comprised of balanced multiple wraplayers oriented so that the number of passes of wrap lying in onedirection is equal to the number of passes of wrap in an oppositeoverlying direction.

The following examples are offered for illustrative purposes only andare not intended to limit the teaching of the present invention.

EXAMPLES Example 1—Composite Film

The ePTFE reinforcing polymer 1 used to make the composite film was madein accordance with the teachings found in U.S. Pat. No. 5,476,589 toBacino, incorporated by reference herewith. Specifically, the ePTFEreinforcing polymer was longitudinally expanded to a ratio of 55 to 1and transversely expanded approximately 2.25 to 1, to produce a thinstrong reinforcing polymer with a mass of approximately 3.5 g/m² and athickness of approximately 6.5 micrometers.

The composite film 3 was made by using a wire-wound rod coating processwhereby a solution of Tecothane TT-1085A polyurethane (Thermedics, Inc.,Woburn, Mass.) and tetrahydrofuran (THF) was coated onto an ePTFEreinforcing polymer. A 3-8 percent by weight solution of TecothaneTT-1085A polyurethane in THF was coated onto the ePTFE reinforcingpolymer to produce a composite film with approximately equal amounts ofTecothane TT-1085A polyurethane as depicted in FIG. 1B on either sideand throughout the ePTFE reinforcing polymer and a total polymer weightapplication of approximately 40-60 percent of the total final compositefilm weight.

Example 2—Bladderless Balloon

The bladderless balloon of the present invention was made by wrapping acomposite film of Techothane TT-1085A polyurethane (Thermedics, Inc.,Woburn, Mass.), and ePTFE reinforcing polymer over a FEP coatedsilver-plated copper core wire (Putnam Plastics LLC, Dayville, Conn.).The wrapped core wire was heat treated and the center wire and FEPcoating were subsequently removed to provide a hollow composite balloontube.

The core wire was a 0.2 mm diameter silver-plated copper wire with afluoroethylene-propylene (FEP) 5100 coating that resulted in a finalwire diameter of 0.394 mm. The ePTFE reinforcing polymer used to makethe composite film is described in Example 1. Specifically, the ePTFEreinforcing polymer was longitudinally expanded to a ratio of 55 to 1and transversely expanded approximately 2.25 to 1, to produce a thinstrong reinforcing polymer with a mass of approximately 3.5 g/m² and athickness of approximately 6.5 micrometers.

The composite film was made by using a wire-wound rod coating processwhereby a solution of Tecothane TT-1085A polyurethane andtetrahydrofuran (THF) was coated onto an ePTFE reinforcing polymer. A3-8 percent by weight solution of Tecothane TT-1085A polyurethane in THFwas coated onto the ePTFE reinforcing polymer to produce a compositefilm with approximately equal amounts of Tecothane TT-1085A polyurethaneon either side and throughout the ePTFE reinforcing polymer and a totalpolymer weight application of approximately 40-60 percent of the totalfinal composite film weight.

The composite film was slit to 5 mm wide and helically wrapped aroundthe 30.5 cm long core wire at a 4 to 5 degree angle from thelongitudinal axis of the wire. The wrapped core wire was heated forapproximately 5 to 30 seconds at 180° C. after wrapping. The core wirewas then wrapped with the composite film in the opposite direction at a4 to 5 degree angle from the longitudinal axis of the wire andsubsequently heated for approximately 5 to 30 seconds at 180° C. Theprocess of wrapping the core wire in opposite directions and heatingafter each pass was repeated until a total of four passes of wrappingwas complete. The wrapped core wire was wrapped around a pin frame withapproximately 30 cm spaces between pins and approximately 180 degrees ofwrap around each pin and tied at the ends before being placed into anoven and heated for approximately 30 minutes at 150° C.

The core wire and the FEP coating over the core wire were removed fromthe composite balloon over wire construction. An approximately 2.54 cmlong section of the composite hollow balloon tube was removed fromeither end of a 30.5 cm long section of the balloon over wireconstruction. The exposed ends of the wire were clamped with hemostatsand pulled by hand until the wire had been stretched approximately 5 cm,at which point it was removed from the center of the tube. The plasticFEP coating was removed in a similar fashion, but was stretchedapproximately 50 cm before it was removed from the balloon. A compositehollow balloon tube was produced with a first layer wrapping material ata low (4 to 5 degree) angle of wrap.

The 2.85 mm inflated diameter by 27 mm long balloon was mounted to a0.36 mm diameter stainless steel hypotube (Creganna Medical Devices,Parkmore West Galway, Ireland) that had been helically wrapped withapproximately three layers of expanded PTFE reinforcing polymer and EFEPfluoroplastic composite with the EFEP layer facing the stainless steeltube. The balloon was attached and sealed to the catheter shaft bywrapping an approximately 5 mm wide ePTFE/eFEP film circumferentiallyaround the balloon approximately five times. One band was wrapped oneach end of the balloon and was centered over the end of the balloon andthe catheter such that it made a seal by contacting both the hypotubeshaft and the balloon as depicted in FIG. 6.

Example 3—Bladderless Balloon with Heat Inflation Technique

The bladderless balloon of the present invention was made by wrapping acomposite film of Techothane TT-1085A polyurethane (Thermedics, Inc.,Woburn, Mass.), and ePTFE reinforcing polymer over a FEP coatedsilver-plated copper core wire (Putnam Plastics LLC, Dayville, Conn.).The wrapped core wire was heat treated and the center wire and FEPcoating were subsequently removed to provide a hollow composite balloontube.

The core wire was a 0.2 mm diameter silver-plated copper wire with afluoroethylene-propylene (FEP) 5100, coating that resulted in a finalwire diameter of 0.394 mm. The ePTFE reinforcing polymer waslongitudinally expanded to a ratio of 55 to 1 and transversely expandedapproximately 2.25 to 1, to produce a thin strong reinforcing polymerwith a mass of approximately 3.5 g/m² and a thickness of approximately6.5 micrometers.

The composite film was made by using a wire-wound rod coating processwhereby a solution of Tecothane TT-1085A polyurethane andtetrahydrofuran (THF) was coated onto an ePTFE reinforcing polymer. A3-8 percent by weight solution of Tecothane TT-1085A polyurethane in THFwas coated onto the ePTFE reinforcing polymer to produce a compositefilm with approximately equal amounts of Tecothane TT-1085A polyurethaneon either side and throughout the ePTFE reinforcing polymer and a totalpolymer weight application of approximately 40-60 percent of the totalfinal composite film weight.

The composite film was slit to 5 mm wide and helically wrapped aroundthe 30.5 cm long core wire at a 4 to 5 degree angle from thelongitudinal axis of the wire. The wrapped core wire was heated forapproximately 5 to 30 seconds at 180° C. after wrapping. The core wirewas then wrapped with the composite film in the opposite direction at a4 to 5 degree angle from the longitudinal axis of the wire andsubsequently heated for approximately 5 to 30 seconds at 180° C. Theprocess of wrapping the core wire in opposite directions and heatingafter each pass was repeated until a total of four passes of wrappingwas complete. The wrapped core wire was wrapped around a pin frame withapproximately 30 cm spaces between pins and approximately 180 degrees ofwrap around each pin and tied at the ends before being placed into anoven and heated for approximately 30 minutes at 150° C.

The core wire and the FEP coating over the core wire were removed fromthe composite balloon over wire construction. An approximately 2.54 cmlong section of the composite hollow balloon tube was removed fromeither end of a 30.5 cm long section of the balloon over wireconstruction. The exposed ends of the wire were clamped with hemostatsand pulled by hand until the wire had been stretched approximately 5 cm,at which point it was removed from the center of the tube. The plasticFEP coating was removed in a similar fashion, but was stretchedapproximately 50 cm before it was removed from the balloon. A compositehollow balloon tube was produced with a first layer wrapping material ata low (4 to 5 degree) angle of wrap.

A 15.25 cm long section of the composite hollow balloon tube was tiedinto a knot and clamped with a hemostat on one end. The opposite end wasslipped through a Qosina male tuohy borst with spin lock fitting(#80343, Qosina Corporation, Edgewood, N.Y.), and a Monoject bluntneedle with Aluminum luer lock hub (model #8881-202389, SherwoodMedical, St. Louis, Mo.) was inserted approximately 2.0 cm into theballoon. The hemostatic valve was tightened to seal the balloon, and wasthen attached to a Balloon Development Station Model 210A (BeahmDesigns, Inc., Campbell, Calif.). The nozzle airflow was set to 25-30units and the temperature was set to 140° C., air pressure to 2.58atmospheres. The air pressure was turned on, the center 40 mm longregion to be inflated was subjected to heat for about 2-3 minutesresulting in a balloon with a diameter of 2.85 mm. The diameter waschecked with a Mitutoyo Laser Scan Micrometer Model LSM-3100 (MitutoyoAmerica Corp, Aurora, Ill.) while in the inflated state. The resultingballoon had a diameter of 2.85 mm and an inflated length of 27 mm.

Using a Monoject blunt needle with Aluminum luer lock hub (model#8881-202389, Sherwood Medical, St. Louis, Mo.) dispensing needle, theballoon was subjected to an internal pressure of 5.44 atmospheres atroom temperature for approximately 1 hour.

The 2.85 mm inflated diameter by 27 mm long balloon was mounted to a0.36 mm diameter stainless steel hypotube (Creganna Medical Devices,Parkmore West Galway, Ireland) that had been helically wrapped withapproximately three layers of expanded PTFE reinforcing polymer and EFEPfluoroplastic composite with the EFEP layer facing the stainless steeltube. The balloon was attached and sealed to the catheter shaft bywrapping an approximately 5 mm wide ePTFE/eFEP film circumferentiallyaround the balloon approximately five times. One band was wrapped oneach end of the balloon and was centered over the end of the balloon andthe catheter such that it made a seal by contacting both the hypotubeshaft and the balloon.

Example 4—Material Properties

All of the experimental runs were performed using Mayer Bar coatingtechnology and direct solution feed to the coating surface.

The Mayer Bar is simply a metal bar with wire windings.

Bars with windings of different wire sizes are used to achieve thedesired thickness in coating. The Mayer Bar is used to apply the wetcoating to the ePTFE membrane. The coating dries with the aid of aninline oven. The finished coated membrane receives a second coatdirectly to the membrane surface. This process provides an even coatingand offers flexibility in the laydown design.

Example 5

The Tecothane 1085 (TT1085) elastomer, used in the coating, is readilysolvated in Tetrahydofuran (THF). THF is characterized by a low vaporpressure, and as expected, a fast evaporation rate. Using this materialthe following results were obtained:

Test Samples:

-   -   Sample 1 Single Sided Coat “2 Passes”    -   Sample 2 Single Sided Coat “4 Passes”    -   Sample 3 Double Sided Coat “2 Passes”    -   Sample 4 Double Sided Coat “4 Passes”        Results: Gross Testing @ Ambient Temperatures:    -   Sample 1: Inflated to 30 atm—no weeping for two minutes.    -   Sample 2: Inflated to 30 atm—no weeping for three minutes.    -   Sample 3: Inflated to 30 atm—no weeping observed until burst at        3 minutes.    -   Sample 4: Inflated to 30 atm—no weeping observed until burst at        7 minutes.        Multiple Inflation Testing:

The following procedure was used for this test. Each unit waspreconditioned at 37° C. for 2 minutes. At 37° C., nine inflations weremade to 18 atm and held for 30 seconds. On the 10^(th) inflation, theunit was removed from the bath, wiped off, and inspected for weeping.

-   -   Sample 1: Weeping observed on the 10^(th) inflation.    -   Sample 2: Weeping observed on the 10^(th) inflation.    -   Sample 3: No weeping observed on 10^(th) inflation. Balloon was        pressurized for 4 minutes.    -   Sample 4: No weeping observed on 10^(th) inflation. Balloon was        pressurized for 45 minutes.

While particular embodiments of the present invention have beenillustrated and described herein, the present invention should not belimited to such illustrations and descriptions. It should be apparentthat changes and modifications may be incorporated and embodied as partof the present invention within the scope of the following claims.

The invention claimed is:
 1. A medical device comprising: an inflatableelement including a composite membrane having a reinforcing layer and apolymer layer over the reinforcing layer, the reinforcing layerincluding a material having a porous microstructure, the polymer layerbeing formed by adding a polymeric material to the reinforcing layersuch that the polymeric material is incorporated into the microstructureof the reinforcing layer and such that the polymeric material forms acoating on the reinforcing layer to define the polymer layer, theinflatable element being a balloon that is configured to inflate to aworking diameter in response to introduction of a fluid into the balloonat pressures greater than a designated pressure before allowing fluidmovement from an interior side to an exterior side of the balloon. 2.The balloon of claim 1, wherein the fluid is a gas.
 3. The balloon ofclaim 1, wherein the fluid is a liquid.
 4. The medical device of claim1, wherein the porous microstructure of the reinforcing layer includes aplurality of nodes and fibrils.
 5. The medical device of claim 1,wherein the reinforcing layer includes ePTFE.
 6. The medical device ofclaim 1, wherein the polymeric material is an elastomeric material. 7.The medical device of claim 6, wherein the elastomeric material is apolyether block amide.
 8. The medical device of claim 1, wherein thepolymeric material is a nylon.
 9. The medical device of claim 1, whereinthe polymeric material is imbibed into the microstructure of thereinforcing layer.
 10. The medical devie of claim 1, wherein thecomposite membrane comprises a tubular structure.
 11. The medical deviceof claim 10, wherein the tubular structure comprises sealed ends. 12.The medical device of claim 1, where in the inflatable element ismounted on an elongate member.